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UCC28070

Dimit Ariti
Prodigy 110 points
Other Parts Discussed in Thread: UCC28070

Hi

We are using the UCC28070 PFC controller to implement an off-line  2kW converter. As we know this controller use current synthesizer to emulate off-time inductor current and  so save one current sensor .What worries me is that the current synthesizer emulates the off time inductor current  based on the input and output  voltage and DC bias inductor value. So for case when the inductor swings significantly (for example from 100uH at full load to 400uH at no load) the current emulation error would be very high. In the other word, when we use the 400uH to calculate the RSYN then at full load when the real inductance is 100uH huge error in current emulation will be made which will affect current control. Can you please comment on this?

Thanks

  • 0
    TI__Mastermind 34465 points

    The equation in the data sheet says to use the max value of boost inductance which is also the no load inductance.

    The current synthesizer use a proprietary method of current control that synchronously monitors inductor current during the MOSFET ON time and emulates downslope during the OFF time. Unfortunately that is all of the information that TI publishes.

    You should use the value of no load inductance in your calculations and you will not have a problem with the value of RSYN

    John Griffin